The invention relates generally to purification of feed gas used for the manufacture of ammonia, and more particularly to improvements in processing of feed gas from which hydrogen rich ammonia synthesis gas and waste gas are derived. The invention specifically concerns treatment of the waste gas to derive useful gas streams, one of which is hydrogen/nitrogen rich, another is nitrogen rich, and another is methane rich. In the prior Purifier Process synthesis gas is separated from the waste gas, which contains excess nitrogen from the feed gas, a small amount of hydrogen, all of the incoming methane and about 60% of the incoming argon. Such waste gas is typically utilized as fuel in a primary reformer.
U.S. Pat. No. 3,442,613 to Grotz describes a process generally known as the Purifier Process, and specifically towards the cryogenic separation process, also known as the cold box, from which synthesis gas for ammonia production is derived. The present invention particularly modifies and improves the coldbox.
Improvements in treatment of the waste gas are needed for enhanced overall process efficiency.